JP3165244B2 - Method for producing biodegradable resin foam - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a biodegradable resin foam, and more particularly to a method for producing starch and ethylene-degradable resin foam.
The present invention relates to a method for producing a disintegratable foamed molded product, such as a sheet, a film, a packaging material (for example, a cup tray, a cushion material, a protective sheet, a protective film), mainly comprising a saponified vinyl acetate copolymer.

[0002]

2. Description of the Related Art In recent years, interest in environmental issues has increased,
For example, there is an increasing demand for the development of technology relating to disposal of synthetic polymer materials such as plastics. As one of them, attention has been focused on biodegradable plastics that can replace conventional petroleum-based plastics.

As a biodegradable plastic, US Pat. No. 4,138,784 discloses a composition comprising starch and an ethylene / acrylic acid copolymer (EAA) disclosed in JP-A-3-313.
No. 33 discloses an ethylene / vinyl alcohol copolymer (E
VOH) and a modified starch. A foamable material using a biodegradable plastic is disclosed in
No. 298,525. The foamable material described in this patent uses water as a foaming agent, but is insufficient in elasticity and compressive strength, for example, as a packing. In addition, Japanese Patent Application Laid-Open No.
No. 8 discloses a foamable material comprising a starch containing water and a synthetic thermoplastic polymer substantially insoluble in water. Japanese Patent Publication No. 4-500833 discloses starch and EA.
A biodegradable plastic foam article comprising A and / or EVOH is disclosed.

[0004] Such a biodegradable plastic foam is produced by adding a plasticizer such as glycerin and a foaming agent to a starch / EVOH composition, melt-mixing and extrusion molding, and having a low density, for example, 0.6 g / m 2. Although a cc foam was obtained, open cells and closed cells were mixed, the size of the cells was uneven, and holes were formed on the entire surface of the molded body, through which the cells had escaped, and the surface was roughened with irregularities Only molded bodies can be obtained.

[0005] In addition, raw starch contains water, and when kneaded under high pressure by an extruder, the starch is gelatinized and melted, and when the melt is left under normal pressure, it expands. When such a foam is to be used as a buffering industrial material, water resistance,
The strength is significantly insufficient.

[0006]

SUMMARY OF THE INVENTION An object of the present invention is to provide a biodegradable resin foam using hydrated starch and hydrated EVOH, which has sufficient water resistance and strength even at a high expansion ratio.

[0007]

Means for Solving the Problems The above-mentioned problem is that the water content is 5%.
Up to 30% by weight of starch-based polymer, water content of 5 to 30% by weight
Comprising a saponified ethylene-vinyl acetate copolymer and a nonionic surfactant, and having an overall water content of 10 to 40.
The present invention solves the above problem by a method for producing a biodegradable resin foam, which comprises melting a composition in an amount of 1% by weight, foaming by combining foaming with water and, if necessary, foaming with a foaming agent.

In the molded article of the present invention, starch and ethylene-vinyl acetate copolymer saponified product (EV) are used as the biodegradable resin.
OH). The weight ratio of starch to EVOH is usually 2:
8 to 8: 2.

Various starches can be used, for example, corn starch, potato starch, sweet potato starch, wheat starch, kissava starch, sago starch, tabioca starch, sorghum starch, rice starch, mame starch, kudzu starch, warabi starch ,
Has-starch, His starch, etc .; Physically modified starch (α-starch, fractionated amylose, heat-moisture treated starch, etc.); Enzyme-modified starch (Hydrolyzed dextrin, Enzymatically degraded dextrin, Amylose, etc.); Chlorinated starch, dialdehyde starch, etc.); chemically modified starch derivatives (esterified starch, etherified starch, cationized starch, cross-linked starch, etc.).

The ratio of ethylene in EVOH is 10 to 6
0 mol%, preferably 20 to 60 mol%. The degree of saponification is at least 60 mol%, preferably at least 90 mol%. EVOH may be used in combination with other copolymerizable monomers, for example, other α-olefins, without impairing the spirit of the present invention.
Ethylenically unsaturated carboxylic acid compounds (acids, anhydrides,
Salts, esters, amides, nitriles, etc.), vinyl ethers, vinyl esters other than vinyl acetate, ethylenically unsaturated sulfonic acid compounds (acids, salts, etc.), and oxyalkylene group-containing monomers. Also, oxyalkylene etherification, cyanoethylation, acetalization,
It may be what has been so-called "post-modified" such as urethanization.

In preparing the composition of the present invention,
Starch polymer having a water content of 5 to 30% by weight, water content of 5 to 3%
0% by weight of EVOH as a starting material, mixed with a nonionic surfactant, and the total water content is 10 to 40% by weight.
The composition is controlled as follows. Starch and EVO
The reason why the water content of H is 5 to 30% by weight and the water content of the whole composition is 10 to 40% by weight is as follows. The water contained in the starch has an effect on melt plasticization,
Since water in OH has an effect of disturbing its crystallinity, plasticization can also be performed immediately. Water is a pre-hydrated starch, EV, rather than added later to the starch, EVOH powder.
OH has better miscibility and gives a foam having excellent physical properties. As the water-containing method, any method such as directly spraying water on anhydrous or low-water content starch-based polymer or EVOH powder, pellets, or the like, or kneading the powder or pellets with water under further heating and pressurization, may be used. Can be adopted. If the water content is lower than the lower limit, uniform foaming becomes difficult in any case, while if the water content is higher than the upper limit, the foam density decreases. When the water content of the whole composition is 30% by weight or more, it goes without saying that water is externally added.

As the nonionic surfactant, known ones can be used, and preferred examples of the surfactant are nonionic surfactants. Among them, polyoxyethylene alkyl phenyl ether, polyoxyethylene alkyl ether, polyoxyethylene polyoxypropylene block polymer, polyoxyethylene alkyl amine ether, ether type nonionic surfactant such as polyoxyethylene lanolin alcohol ether, Particularly preferred for the production method of the present invention.

Known foaming agents can be used,
For example, azodicarbonamide, azobisisobutyronitrile, p-toluenesulfonyl hydrazide, benzenesulfonyl hydrazide are suitable as the decomposition gas generating type foaming agent, and the amount of addition is 0.1 to 100 parts by weight of the foaming composition. 1 to 1.0 part by weight is preferred. In addition, a liquid or gas having a boiling point of 100 ° C. or less can be injected into the melt-kneaded material to foam it.

[0014] In addition to the above components, the foaming composition used in the present invention may contain, depending on the desired properties and use of the foamed molded article,
Various additives such as UV stabilizers, flame retardants, antimicrobial agents, antioxidants, lubricants, etc. can also be added.

In the present invention, the composition can be foamed in the same manner as in the conventional foaming method, and a polyolefin or polystyrene extrusion foaming apparatus can be used.

[0016]

According to the present invention, a biodegradable resin foam having closed cells and a density of 0.2 to 0.02 g / cc can be obtained.

[0017]

Next, the present invention will be described more specifically with reference to examples. Example 1 and Comparative Examples 1-2 12.7% aqueous corn grits, 10 or 30% by weight
Hydrous EVOH (44 mol% of ethylene, degree of saponification 99.4 mol%), nonionic surfactant A polyoxyethylene nonyl phenyl ether (Neugen EA-170, manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), B polyoxyethylene stearyl ether ( Esulgen P320, manufactured by Kao Atlas Co., Ltd.) and a decomposition gas generating agent (azodicarbonamide) were mixed in the amounts shown in Table 1, and the mixture was twin-screw extruder (diameter 30 mm, L / D =
According to 30), it was extruded at a temperature of 160 ° C. from a strand die having a nozzle having a diameter of 5 mm. Table 1 shows the properties of the obtained foam.

[0018]

[Table 1]

Example 2 12.7% water-containing corn grits, 30% water-containing EVOH
(Ethylene 44 mol%, degree of saponification 99.4 mol%) and surfactant A (Neugen EA-170) or C polyoxyethylene lauryl ether (Neugen ET-170,
(Daiichi Kogyo Seiyaku Co., Ltd.) were mixed in the amounts shown in Table 2, and the mixture was mixed with a twin-screw extruder (diameter 30 mm, L / D = 30).
Compound pellets were produced at a temperature of 0 ° C. or lower while suppressing foaming by water. Next, a twin screw extruder (diameter 30 mm, L / D
= 32), butane was extruded from a strand die having a nozzle having a diameter of 5 mm while press-fitting butane with a high-pressure charging pump so as to be 4 parts by weight with respect to 100 parts by weight of the composition.
Table 2 shows the properties of the obtained foam.

[0020]

[Table 2]

Claims (2)

(57) [Claims] 1. A starch-based polymer having a water content of 5 to 30% by weight, a saponified ethylene-vinyl acetate copolymer having a water content of 5 to 30% by weight, and a nonionic surfactant. A method for producing a biodegradable resin foam, comprising melting and foaming a composition having a water content of 10 to 40% by weight. 2. The weight ratio of hydrous starch to hydrous saponified ethylene-vinyl acetate copolymer is from 2: 8 to 8: 2.
The manufacturing method as described.